The area of origin is the area in three-dimensional space where the blood source was located at the time of the bloodletting incident. The area of origin includes the area of convergence with a third dimension in the z direction. Since the z-axis is perpendicular to the floor, the area of origin has three dimensions and is a volume.
The term point of origin has also been accepted to mean the same thing. However, it has been argued, there are problems associated to this term. First, a blood source is not a point source. To produce a point source the mechanism would have to be fixed in three-dimensional space and have an aperture where only a single blood droplet is released at a time, with enough energy to create a pattern. This does not seem likely. Second, bodies are dynamic. Aside from the victim physically moving, skin is elastic and bones break. Once a force is applied to the body there will be an equal and opposite reaction to the force applied by the aggressor (Newton's third law of motion). Part of the force will move the blood source, even a millimetre, and change the origin while it is still producing blood. So the source becomes contained in a three-dimensional volume, or region.
As with the area of convergence, the area of origin is easily calculated by using BPA software. There are other longer, mathematical methods of determining the area or origin, one of which is the tangential method.
IABPA definition:
- Point (Area) of Origin - The common point (area) in three-dimensional space to which the trajectories of several blood drops can be retraced. (see figure 5)
Read more about this topic: Bloodstain Pattern Analysis
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